Questions tagged [antimatter]

Analogous to matter, but with charge of the particles opposite to their ordinary matter counterparts.

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Why is the minimum amount of energy a photon has is equal to the rest energy of one of the particles?

Why is the minimum amount of energy a photon has is equal to the rest energy of one of the particle ? I know that the the minimum possible energy a photon may have is only the rest energy of particles ...
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Why Electron Quantum Field Wants Little Energy But Photon Field Doesn't

In this Quora post: https://qr.ae/pv5tac, it states that the electron quantum field "wants" to reduce the energy it has, so when a particle and an anti-particle interact and the charges ...
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Mass of Antiparticles

Why do the mass of anti-particles have to be exactly equal to the particles ? What I learnt from Srednicki Chapter 23 is that to support charge conjugation symmetry (C-symm) of Lagrangian, mass of ...
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Can interacting QFT be formulated in terms of the path integral or hamiltonian of a relativistic particle? [duplicate]

I read that free QFT need not be formulated in terms of fields. One can derive the same propagator as the path integral of the single free particle action $\int d{\tau} \eta _{\mu \nu} x^{•\mu}x^{•\nu}...
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Experimental results for the measurement of Positron lifetime / Positron decay [duplicate]

It is assumed that the positron, being the antimatter particle of the electron, is stable. I am interested in finding experimental results or experiments which have measured the positron lifetime in a ...
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Does Einstein’s original paper on relativity predict antiparticles and tachyons?

In Einstein’s original paper on relativity (pages refer to this copy) page 149 he gets an initial form of the now known as Lorentz transformation $$\mathbf{x’}=\phi(v) \Lambda \mathbf{x} \tag{1}$$ (I ...
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If the Dirac equation describes charged particles, why is its charge density always positive?

Its charge density is $\psi^\dagger (x) \psi (x)$. This thing is positive for both positive and negative energy Dirac fields. If the charge density is positive, then the total charge is also positive. ...
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Minus sign in Feynman's The reason for antiparticles

I was going through Feynman's lecture on "The reason for antiparticles", which can be found here, and I got a little confused early on. His statement of Eq. 3 seems clear to me, from which ...
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Why are positrons traveling backward in time in Feynman diagrams?

We draw the positron as if it's traveling backward in time. Why? The momentum of the positron is drawn opposite to the time-direction of the diagram. I don't see this having any effect on the ...
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Why is electron-positron annihilation unlikely at high kinetic energies of the positron?

I am wondering about electron-positron annihilation. At https://www.princeton.edu/~romalis/PHYS312/Positron.pdf, I read: During this slowing down process, which is similar to what would be ...
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Is antimatter just matter inverted in an higher dimension? [closed]

This question arose in me after watching https://youtu.be/mmtLgYVEuJs?t=394. The link has a time in it so it takes you to the part I am talking about in the video.
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Matter-antimatter annihilation and CMBR [duplicate]

Does this intensity of microwave background radiation correspond to the huge amount of gamma photons that could be released during the theoretical annihilation of matter and antimatter at the time of ...
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Relativistic particle-antiparticle annihilation

If a particle and antiparticle annihilate they produce photons of certain frequency. My question is about the frequency of the photons if the particles move at relativistic speeds with let say gamma=5....
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How does the wavefunction of an antiparticle differ from that of the particle?

In this question I was answered that the invertion of wave function does not give antiparticles. Then how does the wavefunction of an antiparticle look, given the wavefunction of the corresponding ...
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Could the matter-antimatter symmetry be local rather than universal?

In the observable universe there is an antimatter-matter asymmetry. Are there any theories that propose that this is just a local asymmetry one fluctuation in a universe with an overall symmetry?
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Can positrons attract electrons? [duplicate]

Now, it is established that positrons and electrons have the same mass but opposite charges. Since they have opposite charges, do they create a force of attraction and collide thus annihilating each ...
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Can positrons flow through matter or antimater or both?

Now, I know that a flow of positrons can constitute electricity. But my question is whether positrons can flow through matter conductors like copper or only antimatter conductors.
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What is relation between CPT invariance & Lorentz invariance, and why mass of particle/antiparticle is different in CPT violation?

(1) I read that CPT theorem can be proved with Lorentz invariance. Also, CPT violation implies Lorentz violation. Is CPT invariance equivalent with Lorentz invariance, or just one-side direction holds?...
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If the universe was dominated by antimatter instead of matter, would we physically notice?

I read that antimatter and matter are identical aside from their opposite charge and quantum number. Of course, the mystery of why matter dominates in our universe is an active field of research. But ...
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Why don't we just say that the Klein Gordon equation describes a two component complex function?

These vectors form the basis vectors of the field that the KG equation describes: (for each $\vec{p}$ in $R^3$): $$|e^{i\vec{p} \cdot \vec{x}} , E=+\sqrt {p^2+m^2}\rangle$$ $$|e^{i\vec{p} \cdot \vec{x}...
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Positive charge in electrostatics

We know that all charges are caused by excess or shortage if electrons. Since electrons are negatively charged, it makes sense seeing negative charges in motion which we usually see in electrostatics. ...
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Matter-antimatter and annihilation

In this question, it seems posed how a particle and its anti particle can get close to each to annihilate. One answer proposed that "The force involved in annihilation is normally either the ...
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Doesnt $E=mc^2$ contradict the preservation of charge?

If we say that any mass is the same as a given energy amount, so we in theory could turn any particle into energy, wouldn't that mean we could turn a proton or electron into energy without turning its ...
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18 votes
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Why didn't the Klein-Gordon equation suggest antimatter like the Dirac equation did?

I have heard the story that the Dirac equation suggested the existence of antimatter due to the existence of negative energy solutions. The Klein-Gordon equation also has negative energy solutions. ...
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Electron positron annihilation to more the 3 photons

I understood why a single photon can't be released from the annihilation of an electron and positron and that the common cases are 2 and 3 photons. I have two thing's I'm unsure of: why is the ...
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Antiparticle from the weak charge

For the electromagnetic charge and the colour charge, every particle carrying these charge has an antiparticle having the opposite charge. Why are there no antiparticle from the weak charge?
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Working through the solution of the Ozma problem

I’m trying to work through the Ozma problem and the Wu experiment to get a better handle on parity and I’m being tripped up by something which is almost certainly trivial. I can explain negative ...
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Building things out of antimatter [duplicate]

If we had a significant amount of anti-hydrogen (but not enough to make a star), what would be the most complicated thing we could build out of it, and how would we go about doing so? Edit: I give the ...
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Can Anti-Particle like Anti-Proton give advantage in ADS (Accelerator Driven System) for Neutralizing Nuclear Waste?

I was going through a thesis of Adonai Martinez for "Transmutation of Nuclear Waste in Accelerator-Driven Systems" published in 2004. I saw he used Proton for ADS but it occured to me that, ...
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2 votes
1 answer
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Do matter and antimatter undergo relativistic effects identically?

As far as I know, the Dirac equation describes quantum particles moving at relativistic speeds. Since the dirac equation predicts antimatter as well, we should expect matter and antimatter to undergo ...
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Could the equal amounts of positive and electric charge point to equal amounts of matter and anti-matter?

The universe is electrically neutral because the electric charges of all quarks and leptons cancel. If particles are electrically charged, then there are equal amounts of positive and negative ...
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Proton-antiproton collisions

I have read in lots of different articles that when protons and antiprotons collide, they produce lots of different particles, but mainly (charged) pions. Why is this? Why are they more likely to ...
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Antiparticles vs. physical charges

When one mentions anti-particles, a popular example given is always the opposite electric charge or the color charge. However, if I understand correctly, an anti-particle is a particle with one (or ...
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Can a particle anti-particle pair be created with initial particles conserved?

Is it possible to have a particle collision between 2 particles, have those 2 particles structures conserved, but also create a particle-antiparticle pair in the process? For example, you have a Pion ...
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Confusion about Weinberg's short argument for the existence of antiparticles

In section 5.1 of Weinberg's The Quantum Theory of Fields Volume I, there is a short argument for the existence of antiparticles: It may be that the particles that are destroyed and created by these ...
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Interaction term in Lagrangian implying photon has no antiparticle?

I read that the QED Lagrangian interaction term ($-q\bar{\psi}\gamma^\mu\psi A_\mu$) implies that while electron-positrons come in pairs, a photon does not need to form in a pair (and hence it does ...
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6 votes
2 answers
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Do laws of physics prohibit direct conversion of particles to antiparticles?

Can antiparticles only be created in pair production? How/which laws of physics prohibit direct conversion of say an electron to a positron? A neutron to an antineutron? I have seen a comment that it ...
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Switching particles for antiparticles in Feynman diagrams

While studying, I found a problem involving $e^-\nu_e$ and $e^-\bar{\nu}_e$ scattering, though this could also apply to $e^- e^-$ and $e^- e^+$ scattering if we wanted to keep everything within QED. ...
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Does the Schwinger effect prove matter and antimatter can be created from a vacuum?

Virtual particles or vacuum fluctuations are the pair annihilation/creation of matter and antimatter particles in and out of the vacuum. Theses particles are virtual, but we know they exist because of ...
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What kind of matter is positronium?

What kind of matter is positronium? Normal matter, antimatter, exotic matter or something else? We know: Matter is made up of electrons, protons and neutrons. Antimatter is made up of positrons, ...
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Does Normal matter also include anti-matter and engery?

We have studied approx 4.6% of normal/ordinary matter in the universe and everything till now we observed are a part of this 4.6% I always have doubt. this 4.6% include all the matters and energies ...
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Would light bend the other way, if I use antimatter instead?

Imagine the following setup: an antimatter straw, an antimatter glass filled with antimatter water and we have antimatter atmosphere just in case. My question is: does Snell's law still apply here as ...
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A gram of antimatter reacting with a gram of matter releases Hiroshima-like energy, but is that true in practice?

My understanding is that a particle must meet its antiparticle. So if you a one-gram cube of, say, anti-gold and shot it into a one-gram cube of normal gold, how would you get the particles to come in ...
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Black hole radiation

Black hole radiation in which particle and antiparticle pairs are separated which ultimately leads to the 'evaporation', but why does the negative particle always enters the black hole? Why do the ...
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2 votes
1 answer
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If antiparticles are particles moving back in time, would messages from the future be possible?

So, here's the idea: if Feynman's interpretation of antiparticles is true and antiparticles are particles moving back in time, then they are carrying with them information from the future, no? If that'...
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Most correct intuition for vacuum energies in interacting and non-interacting field theories

It seems like a lot of pop science gets thrown around when explaining vacuum energy. For instance, our QFT lecturer descried the non-interacting field theory vacuum energy as 'purely Heisenberg ...
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Why do we conventionally label anti-particle solutions to Dirac equation with $-p$?

The spinor solutions to the dirac equation tend to be conventionally labelled as $u^s(\vec p)$ for particles and $v^s(- \vec p)$ for anti-particles. Am I correct in thinking that these anti-particles ...
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Euler-Lagrange equation for positron from QED lagrangian

Taking $e<0$ to be the charge of the electron, the Euler-Lagrange equation derived from taking the first variation of the $\psi$ field in the QED lagrangian $${\cal L} = - \frac 1 4 F_{\mu\nu}F^{\...
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Actual physicists: shoot down my hypothesis regarding antimatter, primordial black holes, and the origin of the universe [closed]

Let's get this out of the way up front: I'm no physicist and have no business proposing any of the things I'm about to propose. The likely outcome here is that someone with relevant education can ...
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1 vote
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Spin sign for antiparticle

I have this problem with the sign of the spinor for the antiparticle. In the chiral basis, a spinor is represented by $\psi =(\psi_{L},\psi_{R}$). Now, we consider a particle with mass = 0, so Dirac's ...
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